1. Field of the Invention
The invention relates to hand-held material-dispensing devices such as caulking guns and, more particularly, to a specific type of construction for caulking guns.
2. Description of the Related Art
Hand-held material dispensing devices are well known in the art and generally rely on the action of a piston to push fluid out of a receptacle toward the application area. The movement of the piston is induced by the advancement of a piston rod in the direction of the receptacle, with the piston rod being advanced in the direction of travel by the operator's squeezing of a trigger in engagement therewith.
One such fluid dispenser is disclosed in U.S. Pat. No. 4,461,407 to Finnegan. The Finnegan patent incorporates an automatic pressure release mechanism such as is typical in many caulking guns of the prior art.
In U.S. Pat. No. 4,081,112, issued to Chang, there is disclosed a caulking gun having a forward-biasing spring to urge the trigger back to the cocked position after an application cycle. U.S. Pat. No. 4,033,484, issued to Ornsteen, discloses a hot melt adhesive gun which operates in the conventional manner of the prior art.
U.S. Pat. No. 3,069,053, issued to Nilsson and U.S. Pat. No. 3,189,226, issued to Sherbondy, each show a caulking gun with an alternative piston rod-trigger engagement arrangement. In these references, the trigger urges the piston rod toward the fluid receptacle by means by a ratchet mechanism.
The above-cited patents are merely examples of the plethora of caulking guns in the prior art. As is clear from these examples, that a standard caulking gun provides an arrangement for receiving and retaining a tube of caulking material. The caulk tube has a pointed nozzle at the forward end for dispensing the caulking material as it is pushed from the other end by a driven back plate. A long pusher rod in the body of the caulking gun serves to drive the caulk tube back plate to extrude the caulking material. A trigger mechanism at the back end of the caulking gun serves to advance the pusher rod when activated by a user. A pusher plate is mounted on the forward end of the pusher rod to distribute the forces from the rod to the back plate at the end of the caulking tube.
U.S. Pat. No. 5,887,765, issued to Broesamle, discloses a caulking gun that enables the pressure on the back plate to be eased when an operator is no longer engaging the trigger. Thus, a non-dripping capability is achieved using a mechanism that permits the pusher rod to slide backwards slightly thus stopping further extrusion of the caulking material. However, some types of caulking material for proper application require a continued pressure against the back plate even when the trigger is not being pulled, i.e., the ratchet type of mechanism.
Model CG-00122 caulking gun, manufactured by Great American Manufacturing, Inc. of Sun Valley, Calif. 91352, features a ratchet-type caulking gun wherein a user can select either dripless or non-drip operation. The selector switch changes the angle by which a spring biased plate engages one of the plurality of notches that are provided along the piston rod. This achieves the alternative methods of operation. The barrel cage does not rotate but is riveted to the hand grip housing.
Model SI 300, manufactured by Dripless, Inc. of Santa Rosa, Calif. 95403, is no drip, drip selectable caulking gun. In this model, a dog is provided on the rear of the hand grip housing. This dog is biased by a compression spring that also is exposed on the rear of the hand grip housing so that the mechanism is potentially vulnerable to damage due to being struck or by due to dirt accumulation.
There is not found in the prior art, a caulking gun that can function as either a dripless unit as taught by Broesamle or a drip-type of device as discussed above by merely activating a lever switch on the handle of the caulking gun that selects either a dripless or a standard method of operation and features a rotatable barrel that can be easily removed so that the caulking gun can be more conveniently packed within a tool box.